1. Field of the Invention
This invention relates to the transporting of materials in a clean and sealed environment as the materials are transported between work stations.
2. Description of the Prior Art
Typically, clean room environments require that entire rooms be "clean" and that personnel in the rooms also be "clean" and appropriately garbed. The filtration system requirements are rather strenuous for such clean room activities, and personnel enter and exit through special entryways in order to maintain the integrity of the clean rooms. Elements being processed within the clean room, such as semiconductor wafers or circuit boards, are typically transported by personnel from work station to work station. The wafers themselves are disposed in cassettes, each cassette of which holds a plurality of wafer elements for processing.
Conveyer systems in such clean rooms vary rather greatly. As indicated above, the typical situation is simply the loading of the cassettes full of wafers, or comparable transport elements for integrated circuit boards, and manually carrying to transport between work stations.
U.S. Pat. No. 4,826,360 (Iwasawa et al) discloses a transfer system in a clean room. In the '360 patent, elements being transferred comprise semiconductor wafer cassettes. Transfer tubes are used, and a vehicle is disposed within the transfer tube. A pod moves within the tube on a vehicle. The tube is evacuated to produce a negative pressure so that the vehicle is moved in the transfer tube by negative pressure.
U.S. Pat. No. 4,923,352 (Tamura et al) discloses a clean room system in which semiconductor elements may be processed. The system includes a plurality of filters, blower systems, and a clean room disposed on a second story. A robot is used to transport material being processed between processing stations.
U.S. Pat. No. 4,718,539 (Fukuwatari et al) discloses a conveyor system for transporting parts on a transport pallet. Compressed air is used as the motive force.
U.S. Pat. No. 4,722,659 (Hoyt, III et al) discloses a semiconductor wafer carrier transport apparatus in which semiconductor wafers are disposed in plastic cassettes and the plastic cassettes are transported between carriers.
A robot transport system for transporting semiconductor wafers is disclosed in U.S. Pat. No. 4,904,153 (Iwasawa et al).
U.S. Pat. No. 4,908,533 (Karita et al) discloses a linear motor transport apparatus. Such apparatus may be used in transporting the subject matter of the present invention and related apparatus.
A magnetic levitating transport system is disposed in U.S. Pat. No. 5,180,048 (Kawada et al). Again, such transportation system may be applicable to the apparatus of the present invention.
U.S. Pat. No. 5,363,867 (Kawano et al) discloses a storage area in a clean room. Wafer cassettes are disposed in the storage area.
U.S. Pat. No. 5,417,537 (Miller) discloses a wafer transport apparatus between processing areas. A magnetic levitation system is used for transporting the material carrier between stations.
U.S. Pat. No. 5,443,346 (Murata et al) discloses a system for conveying wafers in a clean room.
U.S. Pat. No. 5,547,328 (Bonora et al) discloses a transport system for transferring articles between controlled environments. The apparatus transports the same type of pods referred to above, in the '360 patent.
Most of the above discussed patents deal with entire clean rooms which require a substantial amount of air filtering, special structural elements, and the like, for such clean rooms. The apparatus of the present invention substantially reduces the complexity of clean room environments by providing smaller sealed environments in which materials being processed, such as semiconductor wafers, may be transported from one processing area to another. Personnel involved in the processing and most of the processing machinery may be disposed outside of the smaller transport clean area. Tubes in which the materials are transported remain relatively sealed with a positive pressure.